Telegraph switching system



June 27, s K| E TELEGRAPH SWITCHING SYSTEM Filed Jan. 30, 1932SUBSCRIBER? I PRINTER l SET-J -J a 0M W W M PR/N TER SUBSCRIBERS LINERELAYS STAES PAT rare

FULLERTON S. KINKEAD, OF NEVT -YOBK, N. Y., ASSIGNOR TO BELL TELEPHONELABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK TELEGRAPH SWITCHING SYSTEM 7 Application filed January 30, 1932.Serial No. 589,840.

This invention relates to printing telegraph switching systems of thetype wherein a central station is adapted to transmit messagessimultaneously to a plurality of printer stations connected thereto.Systems of this type usually comprise a central switchboard having oneor more printer transmitter sets and associated therewith printingtelegraph stations located at a distance from the switchboard andindividually connected thereto by transmission lines. The simultaneoustransmission of signals to a plurality of printer stations connected tothe system, commonly known as broadcasting, is usually effected by theoperation of a key at the switchboard which automatically associateseach printer station with a special broadcast printer set. Several sucharrangements are'disclos-ed in G. S, Vernam Patents 1,762,252, June 10,1930 and 1,798,- 235, March 31, 1931, respectively, and in Patent1,642,037 to Lomax September 13, 1927.

According to the arrangements heretofore employed, a printer station maysignal the operator at the switchboard for disconnection from thebroadcast circuit while still receiving broadcast messages. Thisdisconnection would then be effected by the actuation of one or moreswitching devices at the switchboard. i I

It has been found, however, that for certain business organizations, itis often desirable in artelegraph system provided with the broadcastingfeature, that a particular station receiving the broadcast signalsbeable to disassociate itself from the circuit and automatically to informthe operator at the switchboard of this action. Provided that this couldbe done, it would consequently be advantageous for the switchboardoperator to be able to restore the disabled printer sta-, tion to thereceptive condition without the assistance of the subscriber.

One of the features of this invention enables a printer stationconnected to the switchboard to disassociate itself from thebroadcasting circuit.

Another featureenables the operator at the switchboard to restore thedisabled printer station for receiving the broadcast signals.

The preferred embodiment of this invention is a radial telegraphswitching system comprising a switchboard and a plurality of printerstations connected thereto by means of two-wire lines. Seriallyconnected in said lines and located at the switchboard are jackswhichpermit the insertion of a printer set for individual communicationbetween a printer station and the switchboard. At the switchboard arecircuit means which enable the operator to broadcast signals to allstations connected to the system. Lamp indicators are provided forinforming the operator of the disconnection of a station circuit fromthe broadcasting arrangement. Associated with each line is a switchingdevice for restoring the station circuit for the reception of broadcastsignals.

The line relays and subsidiary apparatus for the subscribers printersets of a broadcasting system are located on a central switchboard.

In the single figure of the drawing, the switchboard relays'andapparatus shown at 1 are associated with the subscribers printer setrepresented by 2. A similar arrangement of switchboard relays andapparatus is indicated at 3 for another subscribers printer set 4:. Anyconvenient number of printer sets may be associated with thebroadcasting system, and their respective line relays can be placed onthe switchboard between relay groups 1 and 3.

The broadcasting circuit is represented as being in its normal conditionfor the transmission of signals by the open and close method, that is,by interrupting continuous current of a given polarity. In order toconserve the battery 5, the switch 6 may be opened during periods ofnon-transmission. Under normal conditions, current from battery passesthrough relay 7 and jack 8 to the broadcasting printer 9. The purpose of7 jack 8 is to provide for the use of an auXiliary printer in caseprinter 9 becomes disabled. Interruptions of this current by the printer9 actuate relay 7 which, since it is polarized by another windingcarrying ourrent from battery 5, causes corresponding interruptions ofthe marking current,'also from battery 5, in the broadcasting loop.These last interruptions cause the actuation of relays and 11 which arepolarized the same as relay 7. When relay 10 is in its normal condition,as is shown in the drawing, a biasing current from battery 5. flowsthrough windings of differential relay 12. Each set of subscribers linerelays, as is indicated in the drawing, contains relays corresponding torelays 11 and, 12 and are operated in a similar manner. Operation ofrelay 11, causes interruptions of the marking current from battery 13 inthe subscribers loop. This marking current passes through differentialrelay 12 to the subs scribers receiving relay 14. Jack 15 is in troducedinto that part of the subscribers loop that is located on theswitchboard in order to provide for the insertion of a print er forindividual communication between the switchboard operator and asubscriber.

Under normal conditions, the effect on differential relay 12* of biasingcurrent from battery 5 is neutralized by marking current from battery 13thus leaving relay 12 unoperated. This allows control current frombattery 5 to flow through the armature and top contact of relay 12 tooperateslow-release relay 17.

To effectdisassociation from the broadcast circuit, the subscribermomentarily operates switch 16 to an open position. This removes fromdifferential relay 12 the influence of battery 13 thus permittingbiasing current from battery 5 to operate relay 12. Theoperation ofrelay 12 removes the influence of battery 5 from relay l7'therebycausing relay 17 to become unoperated The operation of relay 12 alsoallows the control current from battery 5 to now flow through thearmature and bottonrcontact of relay and subsequently through the topcontact and upper armature of relay 17 to ground. At the same time, aparallel path is provided for the control. current from battery 5through signal lamp 18 to the top contact and upper armature of relay 17to ground.

The release of relay 17 alsocauses its lower armature to fall down onthe bottom contact thus completing a short-circuit across thesubscribers loop. This'short-circuit effectually prevents transmissionof broadcast signals as it is tantamount to cutting out relays 11 and 12from the subscribers loop. It,

receptive condition, key switch 19 is moved to the release position atthe right. This allows control current from battery 5 to flow throughthe lower right contact of switch 19 to energize relay 17 When relay 17is operated, the bottom armature removes the short-circuit from thesubscribers loop, restoring it to its normal condition. At the sametime, the top armature opens the circuit through relay 12 causing thearmature of relay 12' to connect with the top contact. The operation ofrelay 17 also causes signal lamp 18 to become extinguished. Controlcurrent from battery 5 is now able to follow its normal path through thearmature and top contact of relay 12 to relay 17. Thus, when switch 19is. subsequently released to the neutral position, relay 17 remainsoperated and the circuit is left in its normal condition.

Under certain conditions, it may be desirable that the subscriber remaindisconnected for a longer length of time. Accordingly, instead of movingswitch 19 to release position, it is moved to the hold position at theleft Control current from battery 5 now follows practically the samepath to operate relay 17 that it followed when switch 19 was in therelease position.v However, the lower left contact of switch 19completes an auxiliary short-circuit across the subscribers loop.Broadcasting to station 2 cannot now take placebecause relay 11 is cutout of the subscribers loop. When it is desired to return the circuit toits normal condition, switch 19' is moved to its neutral position. Thiscauses the lower left contact to open the auxiliary short-circuit andreinstate relay 11 into the subscribers loop.

In case the switchboard operator wishes to hold individual communicationwith station 2, switch 19 is moved to the hold position. Control currentfrom battery 5 is thus provided with a by-path but has no additionalefiect on circuit conditions. 'However, the lower left contact of switch19 closes the auxiliary short-circuit across the subscribers loop andcuts out relay 11 as has been described. The operator can now insertanother print-er into the subscribers loop by means of jack 15 and carryon individual communication.

What is claimed is:

1. A communication broadcasting system having a switchboard, a pluralityof stations conncctable thereto, and instrumentalities at theswitchboard for disassociating a station from the broadcasting circuit.said instrumentalities being operated by the subscriber at theparticular station desiring to be disassociated.

. 2. A communication broadcasting system having a switchboard, aplurality of stations connectable thereto by telegraph lines,instrumentalities at the switchboard for disassociating a station fromthe broadcasting system, said instrumentalities operating in response toa change in the condition of any of the telegraph lines, and connectingmeans whereby the switchboard operator may reassociate a disassociatedstation with the broadcasting system.

3. In a communication broadcasting systern, a central switchboard, aplurality of stations conncctable thereto, and instrumentalities at theswitchboard for disassociating a station therefrom and for lighting asignal lamp to notify the switchboard operator of the disassociation,said instrumentalities being responsive to control means at theparticular station desiring to be disconnected.

4. In a communication system, a switchboard having a circuit forbroadcasting to a plurality of stations, instrumentalities at theswitchboard for disassociating a station from the broadcasting circuitand for lighting a' signal lamp at the switchboard as an indication ofthe disassociation, said instrumentalies being operated in response to adisconnect signal transmitted from the particular station desiring to bedisassociated, and connecting means at tl e switchboard for restoring adisassociated station to the broad ast receptive condition without theassistance of the subscriber.

5. A communication switching system having a central switchboard, aplurality of stations connectable thereto, instrumentalities at thecentral switchboard for disassociating a station from the centralswitchboard and for lighting a signal lamp at the switchboard as anindication of the disassociation, said instrumentalities being operatedby the subscriber at theparticular station desiring to be disassociated,and means whereby the switchboard operator may extinguish the lampWithout restoring the disassociated station to the broadcast receptivecondition.

6. In combination, a communication broadcasting system adapted tobroadcast signals from a single broadcasting station to a plurality ofsubscribers stations over circuits extending from a central switchboard,instrumentalities at the switchboard for the substitution of anauxiliary transmitting station for the broadcasting station, andswitching means for disassociating a subscribers station from thebroadcasting system, said switching means operating in response to acessation in the flow of current in the subscribers loop.

7. A telegraph broadcasting system having a central station from whichtelegraph messages are broadcast, said central station including acentral switchboard, a plurality of subscribers stations each includinga printing telegraph set for connection by telegraph lines to theswitchboard'to receive said messages, and instrumentalities at theswitchboard for disassociating a station from the broadcasting circuit,said instrumentalities being operated by the subscriber at theparticular station desiring to be disassociated.

8. In a telegraph system, a central station 3 from which telegraphmessages are broadcast, said central station including a centralswitchboard having a circuit for broadcasting to a plurality ofsubscribers stations each including a printing telegraph set forconnection by telegraph lines to the switchboard to receive saidmessages, instrumentaiities at the switchboard for disassociating astation from the broadcasting circuit and for lighting a signal lamp atthe switchboard as an indication of the disassociation, saidinstrumentalities being operated in response to a disconnect signaltransmitted from the particular station desiring to be disassociated,and connecting means at the switchboard for restoring a disassociatedstation to the broadcast receptive condition without the assistance ofthe subscriber.

9. In combination, a telegraph broadcasting system adapted to broadcastsignals from a single broadcasting station to a plurality of subscribersstations over circuits extending from a central switchboard at thebroadcasting station, each subscribers station including a printingtelegraph set for connection by means of loops of telegraph lines fromthe subscribers stations to the broadcasting station to receive saidsignals, instrumentalities at the switchboard for the substitution of anauxiliary transmitting station for the broadcasting station andswitching means for disassociating a subscribers station from thebroadcasting system, said switching means operating in response to acessation in the flow of current in the subscribers loop.

In witness whereof I hereunto subscrib my name this 29th day of January,1932.

FULLERTON S. KINKEAD.

